According to the reports, the judge determined that Musk's own tweets violated the law when he implied that workers who unionised would have to give up company-paid stock options.

San Francisco: Tesla and its CEO Elon Musk violated national labour laws when it prevented workers from organising a union at the company's Fremont factory, a California judge has ruled.

Mentioning a controversial Musk tweet on the same issue, Judge Amita Baman Tracy ordered Tesla CEO to hold a public meeting and read aloud the findings to employees at the factory, "informing them the NLRB (National Labour Relations Board) concluded the company had broken the law".

"I recommend that Respondent be ordered to convene its employees and have Elon Musk (or, if he is no longer the chief executive officer, a high-ranking management official), in the presence of security guards, managers and supervisors, a Board agent and an agent 15 of the Union, if the Region and/or the Union so desire, read the notice aloud to employees," the ruling said.

The judge determined that Musk's own tweets violated the law when he implied that workers who unionised would have to give up company-paid stock options, reports TechCrunch.

In his May 20, 2018 tweet, Musk said: "Nothing stopping Tesla team at our car plant from voting union. Could do so tmrw if they wanted. But why pay union dues & give up stock options for nothing? Our safety record is 2X better than when plant was UAW & everybody already gets healthcare."

"Musk's tweet can only be read by a reasonable employee to indicate that if the employees vote to unionise that they would give up stock options. Musk threatened to take away a benefit enjoyed by the employees consequently for voting to unionise," the judge ruled.

The judge also said that Tesla fired one union supporter. Tesla may appeal the ruling although the company did not issue any statement, the report added.